It is commonly known to provide printed circuit boards with heat conducting plated through holes, so called “thermal vias”. Thermal vias improve the heat transmission perpendicular to the printed circuit board. The thermal conductivity of cost-efficient basis materials, such as FR4 with 0.3 W/mK, is regarded as being too marginal for a cooling of electronic components. The primary objective of using thermal vias is an improvement of thermal conductivity; they utilize the high heat conductance value (300 W/mK) of copper, the material of a typical plated through hole. By means of a dense arrangement, for example having a hexagonal raster of 0.5 mm and a diameter of the vias of 0.25 mm, up to 10% of copper may be effectively realized in the printed circuit board. From this follows a thermal conductivity of 30 W/mK perpendicular to the printed circuit board. It is also commonly known to provide printed circuit boards with a metal core and thick copper allowing for a higher lateral thermal conductivity. For this, copper or aluminum sheets or copper layers strengthened up to 400 μm are included in the printed circuit board. In conjunction with a print of heat conducting paste a heat reduction may thus be achieved and in certain cases the application of additional heat sinks may be avoided, if the generation of heat by the electronic components does not become too high.
DE 20 2004 006 870 U1 discloses a electrical printed circuit board comprised of at least one dielectric supporting layer and a conductive pattern attached at least on one side thereof representing a electrical circuit with at least one laminary heat conducting block (heat sink) inserted into a continuous recess of the supporting layer and consisting of a metallic substance, which comprises at least one heat conducting contact with the conductive pattern and whose front faces substantially extend flush with the levels of the top side as well as the lower side of the printed circuit board, characterized in that at least one front face of the heat conducting block is coated with a surface metallization layer extending beyond the boundary of the recess, that the inner walls of the recess are evenly coated with a metallization layer and that the heat conducting block comprises at least one heat conducting contact with this metallization layer.
LED light sources (such as LED chips or a LED submount) and if applicable respective electronic components (such as driver components), due to their high heat development, heretofore are simultaneously electronically connected to a printed circuit board and thermally connected to a cooling system. In order to connect to the cooling system the printed circuit board for the most part is provided with a large area heat sink on its back side. However, such solutions are comparably inefficient and large in volume.